EP 0 732 779 B1 discloses crimping pliers for crimping a wire end sleeve with a conductor with removed insulation. The crimping pliers comprise a pliers head. The pliers head is built with a base body. The base body is rigidly connected with a rigid hand lever. A pivoting ring is pivotable with respect to the base body around a die axis. In the region of its inner ring the pivoting ring comprises radial recesses building a kind of spline profile. Six crimping plugs are regularly distributed at locations around the die axis. The die plugs are each pivotably linked with a pivoting bolt held by the base body. In the end region facing away from the die the crimping plugs are each housed in the recesses of the spline-profiled recesses of the pivoting ring. The pivoting movement of the pivoting ring causes a common pivoting of the crimping plugs. The die is built from the radial inner die surface of the crimping plugs and is almost closed in the circumferential direction. The cross-sectional area of the die reduces with the pivoting movement of the pivoting ring and the caused rotation of the crimping plugs so that the crimping of the wire end sleeve is caused. The actuation of the pliers head by causing a relative pivoting movement of the pivoting ring with respect to the base body is done by a drive bolt or pivoting bolt linked with the pivoting ring. The drive bolt or pivoting bolt is a component of a pivoting link. By the pivoting link an end region of a movable hand lever is linked at the pivoting ring. At a location with a small distance from the afore mentioned pivoting link a pressure lever is linked at the movable hand lever by another pivoting link. This pivoting link builds a toggle joint. In the end region facing away from the toggle joint the pressure lever is linked at the fixed hand lever. For building this link, the pressure lever forms a bearing sphere which is housed in a bearing shell formed by the rigid hand lever. A return spring acting in opening direction of the crimping pliers is with one spring base directly linked at the pivoting ring, whereas the other spring base of the return spring is linked at the fixed hand lever. Remote from the connecting region between the toggle joint and the bearing sphere the pressure lever comprises a circumferential section comprising teeth which cooperate with a latching element. The latching element is pivotably linked at the movable hand lever. The latching element is biased towards an equilibrium position by a spring acting between the latching element and the movable hand lever. With the teeth of the pressure lever and the latching element a forced locking mechanism is built. Once arriving at a crimping step of the crimping pliers the forced locking mechanism guarantees that the reached crimping step is also secured when reducing the actuation forces applied upon the hand levers wherein no opening movement of the pliers head takes place. Instead, an opening movement is only possible if the pressure lever has completely passed the predetermined overall crimping stroke.
EP 0 732 779 B1 describes the problem that generally for crimping pliers with a forced locking mechanism the forced locking mechanism defines an end state which correlates with a predetermined end size of the die. When crimping workpieces of different sizes (e.g. due to tolerances from the manufacturing of the workpiece or due to the use of different types of workpieces) with the crimping pliers, the crimping process ends with the afore mentioned predetermined end size of the die. Accordingly, independent from the size of the workpiece the overall crimping stroke is always the same, whereas the effective crimping forces depend on the size of the workpiece. This might in some case deteriorate the uniformity and quality of the crimping result. It is also possible that damages up or even a breakage of components of the crimping pliers result which is due to an overload.
On this background, EP 0 732 779 B1 proposes not to rigidly support the bearing stud of the pressure lever. Instead, according to EP 0 732 779 B1, in the connecting region between the base body and the bearing shell the fixed hand lever is flexible. Dependent from the amount of the effective crimping force, the bearing shell is deformed. The deformation of the bearing shell provides a movement of the hand levers towards each other without a pivoting movement of the pivoting ring relative to the base body without any further reduction of the cross-sectional area of the die. Accordingly, for a larger workpiece according to EP 0 732 779 B1 it is possible to arrive at an end state of the forced locking mechanism. Here, in the beginning in a crimping stroke the crimping plugs move towards each other in an extent which is smaller than the extent of the movement of the crimping plugs towards each other for a smaller workpiece. An additional movement of the hand levers towards each other then does not result in an additional movement of the crimping plugs towards each other but in an elastic deformation of the fixed hand lever. Also a superposition of the movement of the crimping plug and the deformation of the fixed hand lever is possible.
For providing a sufficient elasticity for the support of the bearing shell, the fixed hand lever is built with two hand lever parts which are connected with each other in an end region having a V-shape. In another end region one hand lever part builds the bearing shell, whereas the end region of the other hand lever part is fixedly linked with the base body of the pliers head or builds the same. The two hand lever parts are flexible. For this purpose, the hand lever part forming the bearing shell is tapered towards the bearing shell, whereas the other hand lever part comprises a constriction or narrowing having an extent so that the constriction or narrowing is elastically deformable by applied hand forces. The rigid connecting region of the two V-shaped hand lever parts has to be designed such that in this end region the actuation of the crimping pliers is possible by the hand of the user. According to EP 0 732 779 B1, the connection of the two hand lever parts is provided by a connection with a positive lock via a transverse bolt and knops embossed in longitudinal direction. The effect caused by the elastic support of the pressure lever in the region of the bearing shell is in EP 0 732 779 B1 also denoted as “force-displacement-compensator”.
Further prior art concerning a pliers head with an actuation of more than two crimping plugs by a pivoting movement of a pivoting ring is disclosed in the patent publications DE 101 40 270 B4 and DE 10 2005 003 615 B3. However, in these patent publications the crimping plugs are not pivotably held at the base body but are guided for a displacement in radial inner direction relative to the base body. Here, a differing drive kinematic is used for the actuation of the pliers head.
Also EP 0 158 611 B1 proposes to elastically support the linking point of the pressure lever at the fixed hand lever. This is done by the arrangement of a bearing bolt supporting the pressure lever in an elongated hole of the fixed hand lever. The bearing bolt is able to move along the elongated hole under the bias of a spiral spring.
DE 31 09 289 C2 also proposes to elastically support a pressure lever (here for crimping pliers with scissor-like crimping jaws). In this case, the elastic support of the pressure lever is provided by a narrowing in the form of a slot of the hand lever in the region of the linking point for the pressure lever. The slot results in a bifurcation of the fixed hand lever. In the region of the bifurcation the material of the fixed hand lever comprises a reduction of the cross-section. The reduction of the cross-section causes an elastic deformation of the fixed hand levers for the effective crimping forces.